amino acids Flashcards
What do amino acids consist of?
A central carbon group covalently linked to a carboxyl group, an amino group, and an R sidechain.
There are 20 types of amino acids.
What are the families of amino acids?
Basic positive
Acidic Negative
Uncharged Polar
Nonpolar
What are peptide bonds?
They link amino acids to each other via condensation reactions, where water is released from the chain as a byproduct.
Peptide bonds don’t rotate due to being planar and having partial double bond character.
Primary Structure
Sequence of amino acids. Amino acid sequence controls more complex structure.
What affects protein shape?
Noncovalent bonds and hydrophobic forces affect shape.
A protein will have polar molecules on the outside with a hydrophobic core region that contains nonpolar side chains
Secondary Structure
Stretches of a protein that form alpha helices and beta sheets.
alpha helix
Polypeptide chain twists to form a cylinder.
Amino group forms a H-bond with carboxyl group at n+4 position.
Beta sheet
Each strand of the sheet has a pleat every 2 amino acids. H bonds hold adjacent strands together.
Tertiary Structure
3d arrangement of secondary elements connected by loops.
Stabilized by noncovalent interactions and disulfide bonds.
Amino Acid location on Tertiary Structure
nonpolar tend to be interior, polar charged tend to be on surface, polar uncharged found interior and on surface.
Fibrous
polypeptide chains composed primarily of one type of secondary structure.
Provide strength and stability. Usually insoluble in water due to large number of hydrophobic amino acids.
Globular proteins
compact shape with an irregular surface.
may be composed of multiple domains ( stretches of amino acids capable of folding independently of the rest of polypeptide, may even function independently.),
typically water soluble.
What role do disulfide bonds play?
They are covalent bonds that crosslink parts of a chain or two different chains via adjacent cysteine side chains. Stabilize tertiary and quaternary protein structure.
Quaternary structure
protein composed of multiple polypeptides (subunits). Subunits can be identical or different. Stabilized by noncovalent interactions and disulfide bonds.
How does alzheimers relate to proteins?
Alzheimer’s is an amyloid disease where the protein partially unfolds, beginning to inappropriately associate and form fibrils. Fibrils are plaques commonly observed in brains of patients.
